Many conventional mechanical systems are monitored to determine operating conditions such as pressure, temperature, vibrations, etc. However, in many systems it is desirable to monitor and measure operating conditions at locations in the system where it is extremely difficult to do so. For example, the measurement environment may be a harsh environment in which sensors are unable to operate reliably. For example, monitoring a gas turbine engine presents unique challenges due to the harsh environmental conditions of the engine, i.e., high temperatures, high pressures, and high vibrations a sensor is subjected to during operation of the engine. In mechanical systems, conventional sensors used to monitor operating conditions in harsh environments often fail at an extremely high rate and lead to high maintenance costs in maintaining the mechanical system due to limits associated with the materials required to construct the sensors. In addition, conventional sensors typically require a variety of materials bonded together, and the varying limits associated with the varying materials may further complicate sensor design, and may also lead to increased failure rates due to some required materials having different thermal expansion rates that can introduce large mechanical strains. In addition, some conventional sensors such as thermocouples can be susceptible to sensor drift in harsh environments.
Conventional methods of dealing with the above issues typically involve acknowledging the limits associated with a sensor, the lifetime of the sensor, and that its lifetime and measurement capabilities are limited by the environment within which it is configured. In some systems, conventional methods of dealing with the above issues typically involve fixing a sensor in a location remote from the desired sensing location and estimating operating conditions at the desired sensing location based on the data collected from the remote position.
Sensors have also been developed utilizing a single material to minimize thermal strains and the challenges associated with bonding dissimilar materials, as well as one or more wires coupled to and/or integrated with the sensors and functioning as active mechanical waveguides through which ultrasonic signals may be propagated and sensed to measure the environmental conditions, e.g., pressure, force, strain, temperature, etc., to which the sensors are subjected. In some instances, the wires may be tensioned and/or coupled to one or more diaphragms such that pressure differences or other forces deflect the diaphragms and induce varying tension and/or elongation of the wires, which in turn vary the ultrasonic signal transmission characteristics of the wires in a measurable manner.
Nonetheless, in some instances, various environmental conditions can contribute to the ultrasonic signal transmission characteristics of the wires used as active mechanical waveguides, resulting in a need to compensate for some environmental conditions when attempting to measure other environmental conditions.
In addition, in some instances, generating and detecting ultrasonic energy in the wires used as active mechanical waveguides, and in particular, transmitting ultrasonic energy to an active waveguide wire from a transducer and/or receiving ultrasonic energy from an active waveguide wire with a receiver can be subject to energy losses that reduce signal strength and lower the signal to noise ratio.
Consequently, there is a continuing need for improved sensors and sensing methods to address these and other difficulties with conventional sensor technology.